Area and perimeter of a 2D shape
Pick a 2D shape, enter its measurements, and get the area and perimeter with the shape drawn to scale.
Result
78.5398 units²
Circumference 31.4159 · Diameter 10
Area = π r² = π × 5² = 78.5398
How is this calculated?
Using the tool
Pick a shape, enter its measurements, and see the area and perimeter — with the shape drawn to scale. Lengths are in whatever unit you use; area comes back in square units.
The formulas
A circle's area is π r² (circumference 2π r). A rectangle's is width × height. A trianglefrom its three sides uses Heron's formula: with s = (a + b + c) ÷ 2, area = √(s(s−a)(s−b)(s−c)); the sides also give its type. A trapezoid's area is the average of the two parallel sides times the height: ((a + b) ÷ 2) × h. A regular polygon of n equal sides has perimeter n × s, interior angles of (n − 2) × 180° ÷ n, and area (n s²) ÷ (4 tan(180°/n)).